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Abstract

Heavy metal concentrations in some biotic and abiotic components of the Olezoa wetland complex (Yaoundé-Cameroon, West Africa).

Abstract

Concentrations of cadmium (Cd), copper (Cu), zinc (Zn) and lead (Pb) in water, sediments, fish organs and plants from two ponds of the Olezoa wetland complex were analysed. Plants investigated were Cyperus papyrus, Enydra fluctuans, Ipomoea aquatica and Echinochloa pyramidalis. The fish species studied was the walking catfish Clarias lazera and the heavy metal concentrations were measured in the digestive tract, gills, flesh and liver. Average concentrations in water were 6×10-2 ppm for Cd, 14.53 ppm for Cu, 2.88 ppm for Zn and 17.69 ppm for Pb. These values were low compared to those recorded in the sediments, plants and fish organs. Results revealed an increase of heavy metal concentrations from water to plants and fish organs, with magnification factors ranging from 580 to 5700 and from 577 to 8173, respectively. In the sediments and the floating mat of the eutrophic fish ponds, these factors ranged from 491 to 1065 and 624 to 758, respectively. In the fish organs, particularly, the following accumulation gradients were foreseen: gills → flesh → digestive tract → liver for Cd and Pb; and flesh → gills → digestive tract → liver for Cu and Zn. The four plants studied appeared to be good candidates for phytoremediation of water metal pollution. The quantity of heavy metals in this wetland complex is considerable and will constitute a potential hazard for biota.